struct f
{
  struct _
  {
    template< class x_1, class=void>
    struct app
    {
      struct _
      {
        template< class x_2, class=void>
        struct app
        {
	  ...
	   .
	   .
	   .	   
	  ...
	      struct _
	      {
		template< class x_N, class=void>
		struct app
		{
		  struct _:  ||e||
		  {
		    typedef typename ||e||::value value;
		  };
		};
	      };
	   ...
	   .
	   .
	   .	   
	  ...
        };
      };
    };
  };
};

